This invention relates to the field of colorants, especially for use in recording fluids for writing and recording instruments, for example for ink-jet processes.
By ink-jet process is meant a recording system where droplets of ink are sprayed from a small nozzle onto a recording material, for example paper, under electronic control. The applied ink droplets adhered on the recording material and so depict the desired information. In practice, two methods are used today for generating and directing the ink droplets: the continuous stream process, in which a continuous spray of ink droplets is produced, the unneeded droplets being deflected into reservoir vessel for recycling, and the drop-on-demand process, where ink droplets are produced only when actually needed for writing. Generation of droplets may be effected by briefly raising the pressure, for example by means of a piezo crystal, in an ink chamber equipped with a small nozzle. There are also systems where the spray of ink droplets is produced by supplying thermal energy.
Regardless of the operating principle underlying an ink-jet recording system, the ink used has to meet certain requirements. The ink composition has to have carefully harmonized physical properties such as surface tension, viscosity and electrical conductivity to render it suitable for generating the droplets and controlling their direction of flight. Another important requirement is that the ink may not form any solids, even on evaporation of any constituent of the recording fluid or when the chemical composition of the ink changes during storage, during recording or during a recording pause. Furthermore, the image once recorded shall possess high water resistance, lightfastness and abrasion resistance (EP-A-0 823 233 and U.S. Pat. No. 5,188,664). Prior art inks, especially aqueous inks, however, have the disadvantage of tending to smudge on the recording material when they are moistened. A further disadvantage is that prior art inks usually fade quickly on exposure to light or mechanical abrasion.
Considering ink formulation requirements for multicolor printing, an additional problem is that the dyes used in the inks must correspond very exactly to the three color primaries yellow, magenta and cyan. The choice of suitable dyes is constrained not only by the hue needed, but also by the necessary cleanness of hue and the desire for brilliant color reproduction. Hitherto it has not been possible to develop an ink composition that possesses all the desired properties to the ideal degree and can be successfully used in commercial practice. Take magenta inks as an example. Conventional inks based on water-soluble magenta dyes utilize for example direct dyes, such as C.I. Direct Red 1, 11, 37, 62, 75, 81, 87, 89, 95 and 227. Inks prepared from direct dyes have excellent water resistance owing to the substantivity of direct dyes, but also two disadvantages: the nozzles tend to become clogged with precipitated dye during continuous printing or in intermittent use because of the low solubility in water. Secondly, aggregation is increasingly observed, which leads to dull hues and hence to unsatisfactory color reproduction.
On the other hand, the use of acidic dyes, for example C.I. Acid Red 1, 8, 52, 87, 94, 115, 131, 144, 152, 154, 186 and 245, has also been investigated, with the result that good color reproduction is indeed achieved, but the durability of the printed images is poor because of the low light and water resistance.
DE-A-3 614 462 and DE-A-3 320 373 disclose recording fluids which may contain reactive dyes. However, prints with water-soluble reactive dyes of the chlorotriazinyl or xcex2-sulfatoethylsulfonyl type, however, usually do not possess optimal water resistance, an additional adverse effect being the formation of chloride or sulfate ions through hydrolysis of the reactive groups.
As well as dyes, ink-jet ink colorants also include highly lightfast pigments, for example C.I. Pigment Red 122, C.I. Pigment Red 176, C.I. Pigment Red 184, 185 or C.I. Pigment Red 269. The disadvantage is that the prints obtained lack brilliance.
There is consequently a need for improved recording fluids which are superior to prior art magenta inks especially in hue, storage stability and water resistance and also have the other properties required for the ink-jet art.
It has been found that, surprisingly, the stated requirements are met on using the hereinbelow defined water-soluble dyes of the formulae (1) and (2) as mixtures.
The present invention provides a dye mixture consisting essentially of C.I. Acid Red 289 of the formula (1) and a compound of the formula (2) in a weight ratio of 1:100 to 100:1, based on dry weights, 
where
x is SO2R1,
Y is H, alkyl, alkoxy, preferably H, (C1-C4)-alkyl, (C1-C4)-alkoxy;
R1 is OH, CHxe2x95x90CH2, CH2CH2OR2, CH2CH2NR3R4 and CH2CH2SR5,
R2 is H, SO3M or (C1-C6)-alkyl, which may be substituted by one or more, for example 1, 2 or 3, substituents selected from the group consisting of OH, NH2, COOM and SO3M;
R3 and R4 are independently H, (C1-C6)-alkyl, which may be substituted by one or more, for example 1, 2 or 3, substituents selected from the group consisting of OH, NH2, COOM and SO3M, (C1-C6)-acyl, C6-C10-aryl or halogen-substituted C6-C10-aryl;
R5 is (C1-C6)-alkyl, which may be substituted by one or more, for example 1, 2 or 3, substituents selected from the group consisting of OH, NH2, COOM and SO3M, (C1-C6)-acyl, C6-C10-aryl or halogen-substituted C6-C10-aryl;
M1 is Cu, Co, Ni, Fe, Cr or ⅔ Al; and
M is hydrogen, a monovalent metal cation, one equivalent of a polyvalent metal cation or an ammonium ion which may be substituted by (C1-C4)-alkyl, (C1-C4)-alkoxyalkyl or hydroxy-(C1-C4)-alkyl.
M is preferably hydrogen, sodium or potassium.
M1 is preferably Cu.
The compound of the formula (2) where SO2R1 is meta to the azo linkage and Y is H and also where R1 is xcex2-sulfatoethyl and M1 is Cu, is known as C.I. Reactive Red 23.
Preference for the purposes of the present invention is given to a mixture of C.I. Acid Red 289 and C.I. Reactive Red 23.
Preferred mixing ratios, based on dry weights, are between 1:10 and 10:1, especially between 1:4 and 4:1.
The dye mixture of the invention may additionally contain a shading colorant, preferably selected from the group consisting of C.I. Direct Red 1, 11, 37, 62, 75, 81, 87, 89, 95, 227; C.I. Acid Red 1, 8, 52, 87, 94, 115, 131, 144, 152, 154, 186, 245 and 249; C.I. Pigment Red 122, 176, 184, 185 and 269. The shading colorant is preferably present in an amount of 0.001 to 5% by weight, especially 0.01 to 1% by weight, based on the dry weight of the total mixture.
A possible process for preparing the dye mixture of the invention comprises the dyes of the formulae (1) and (2) and optionally the shading colorant being mixed with each other in the stated mixing ratios, in powder form, in dissolved form, in the form of a water- or solvent-moist presscake or in the form of a masterbatch.
Dyes of the formula (2) are preparable as described in as yet unpublished German patent application 101 06 682.1.
The dyes may also be prepared by the continuous mixing of equivalent amounts of the starting materials in the form of aqueous acidic or aqueous alkaline solutions in for example mixing nozzles and continuous reactors with or without a supplementary reaction phase in a reaction vessel.
The present invention also provides for the use of the disclosed mixtures for dyeing and printing natural and synthetic fiber materials (e.g. polyester, silk, wool, blend fabrics), especially for recording script and images on various recording media, and also for coloring paper or celluloses in the pulp.
For use in recording fluids, the described dyes are worked up in a manner appropriate to the stated requirements. The dyes may be isolated from the initially obtained, preferably aqueous, reaction mixtures by salting out and filtration or by spray drying, optionally after partial or complete desalting by means of membrane filtration. However, it is also possible to dispense with any isolation and to convert the dye-containing reaction mixtures directly into concentrated dye solutions by addition of organic and/or inorganic bases, possibly humectants, preservatives and optionally after partial or complete desalting by means of membrane filtration. Alternatively, complex dyes may also be used as presscakes (including in flushing processes), where appropriate or as powders. Advantageously, the dye mixtures of the invention are used in substantially salt-free form, i.e., free of NaCl or other customary inorganic salts formed in the synthesis of the dyes.
Useful inorganic bases for concentrated dye solutions include for example lithium hydroxide, lithium carbonate, sodium hydroxide, sodium bicarbonate, sodium carbonate, potassium hydroxide, potassium carbonate and ammonia. Useful organic bases include for example monoethanolamine, diethanolamine, triethanolamine, 2-aminopropanol, 3-aminopropanol, dipropanolamine, tripropanolamine, N-methylaminoethanol, N,N-dimethylaminoethanol, N-phenylaminopropanol, ethylenediamine, tetramethylethylenediamine, tetramethylpropylenediamine, tetramethylhexylenediamine, diethylenetriamine, triethylenetetramine, triethylamine, diisopropylethylamine and polyethylenimine.
Useful humectants for concentrated dye solutions include for example formamide, urea, tetramethylurea, xcex5-caprolactam, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, butylglycol, methylcellosolve, glycerol, N-methylpyrrolidone, 1,3-diethyl-2-imidazolidinone, sodium xylenesulfonate, sodium cumenesulfonate and sodium butylmonoglycol sulfate.
The dye mixtures of the invention are particularly useful for preparing recording fluids, especially aqueous and nonaqueous inks for the ink-jet printing process, and also for ink-jet inks which work according to the hot-melt process or are based on microemulsions, but also for other printing, duplicating, marking, writing, drawing, stamping or registering processes.
The present invention also provides recording fluids which contain a dye mixture according to the invention and optionally other colorants for shading. Such shading colorants are advantageously present in an amount of 0 to 20% by weight, preferably 0.01 to 10% by weight, especially 0.1 to 5% by weight, based on the total weight of the recording fluid. The composition of the recording fluid has to be adapted to the particular use.
Recording fluids according to the invention contain in general in total 0.1 to 50% by weight of said mixture of dyes (1) or (2) and, if present, of the shading colorant, reckoned as dry weight, 0 to 99% by weight of water and 0.5 to 99.5% by weight of organic solvent and/or humectant. In a preferred embodiment, the recording fluids contain 0.5 to 15% by weight of said dye mixture, reckoned as dry weight, 35 to 75% by weight of water and 10 to 50% by weight of organic solvent and/or humectant; in another preferred embodiment 0.5 to 15% by weight of said dye mixture, reckoned as dry weight, 0 to 20% by weight of water and 70 to 99.5% by weight of organic solvent and/or humectant.
Water used to prepare the recording fluids is preferably used in the form of distilled or demineralized water. The solvents and/or humectants in the recording fluids can be an organic solvent or a mixture of such a solvent, in which case water-miscible solvents are preferred. Useful solvents include for example mono- or polyhydric alcohols, their ethers and esters, e.g., methanol, ethanol, propanol, isopropanol, butanol, isobutanol; di- or trihydric alcohols, especially of 2 to 6 carbon atoms, e.g., ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2,6-hexanetriol, glycerol, diethylene glycol, dipropylene glycol, triethylene glycol, polyethylene glycol, tripropylene glycol, polypropylene glycol; lower alkyl ethers of polyhydric alcohols, for example ethylene glycol mono-methyl, -ethyl or -butyl ether, triethylene glycol mono-methyl or -ethyl ether; ketones and ketone alcohols such as for example acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, methyl pentyl ketone, cyclopentanone, cyclohexanone, diacetone alcohol; amides, for example dimethylformamide, dimethylacetamide, N-methylpyrrolidone; also urea, tetramethylurea, thiodiglycol, xcex5-caprolactam.
The recording fluids of the invention may further contain customary additives, for example preservatives, cationic, anionic or nonionic surface-active substances (surfactants and wetting agents) and also viscosity regulators, for example polyvinyl alcohol, cellulose derivatives, or water-soluble natural or synthetic resins as film formers or binders to enhance the adhesion and abrasion resistance. They may further contain photostabilizers.
They may also contain amines, for example ethanolamine, diethanolamine, triethanolamine, N,N-dimethylethanolamine or diisopropylamine, to raise the pH of the recording fluid, normally at 0 to 10% by weight, preferably 0.5 to 5% by weight, based on the total weight of the recording fluid.
The recording fluids for the ink-jet printing process may have added to them, depending on the form of this printing process, for example as continuous jet, intermittent jet, pulsed jet or compound jet process, further additives, for example to buffer the pH, to adjust the electroconductivity, the specific heat, the thermal expansion coefficient and the conductivity. Recording fluids according to the invention in storage are not prone to the formation of precipitates that leads to fuzzy prints or nozzle cloggage.
The recording fluids of the invention have viscosity and surface tension values which are within the ranges suitable for the ink-jet processes. They provide prints of high optical density with excellent light- and waterfastness.
Furthermore, the magenta dye mixtures of the invention may be used as an ink set in combination with black, yellow and/or cyan recording fluids. The yellows and cyans involve not only dyes, for example C.I. Acid Yellow 17, C.I. Acid Yellow 23, C.I. Direct Yellow 86, C.I. Direct Yellow 98, C.I. Direct Yellow 132, C.I. Reactive Yellow 37, C.I. Acid Blue 9, C.I. Direct Blue 199, but also pigments, such as C.I. Pigment Yellow 17, C.I. Pigment Yellow 74, C.I. Pigment Yellow 83, C.I. Pigment Yellow 97, C.I. Pigment Yellow 120, C.I. Pigment Yellow 139, C.I. Pigment Yellow 151, C.I. Pigment Yellow 155, C.I. Pigment Yellow 180, C.I. Pigment Violet 19, C.I. Pigment Blue 15, C.I. Pigment Blue 15:3, C.I. Pigment Blue 15:4. The blacks are C.I. Food Black 1 and 2, C.I. Direct Black 168, C.I. Direct Black 195, C.I. Reactive Black 8, C.I. Reactive Black 31, C.I. Sol. Sulfur Black 1, Carbon Black. In the case of reactive dyes, even dyes which have been reacted with nucleophiles can be used in ink sets.
Moreover, the dye mixtures of the invention are useful as colorants in the electrophotographic toners and developers, for example one- and two-component powder toners, magnetic toners, liquid toners, polymerization toners and other specialty toners.
Typical toner binders are addition polymerization, polyaddition and polycondensation resins, such as styrene, styrene-acrylate, styrene-butadiene, acrylate, polyester, phenolic and epoxy resins, polysulfones, polyurethanes, individually or in combination, and also polyethylene and polypropylene, in or to which further ingredients, such as charge control agents, waxes or flow agents, may be present or added subsequently. Dye mixtures according to the invention are further useful as colorants in powders and powder coating materials, especially triboelectrically or electrostatically sprayed powder coating materials, which are used to coat the surfaces of articles made for example of metal, wood, plastic, glass, ceramic, concrete, textile material, paper or rubber. Powder coating resins employed are typically epoxy resins, carboxyl- and hydroxyl-containing polyester resins, polyurethane resins and acrylic resins together with customary curing agents. Combinations of resins are also used. For instance, epoxy resins are frequently used in combination with carboxyl- and hydroxyl-containing polyester resins.
The dye mixtures of the invention are also useful as colorants for color filters, for additive as well as subtractive color generation (P. Gregory xe2x80x9cTopics in Applied Chemistry: High Technology Applications of Organic Colorantsxe2x80x9d Plenum Press, New York 1991, page 15-25), and also as colorants in electronic inks for electronic newspapers.
In the above-described application areas too, the mixtures of the dyes (1) and (2) may be additionally shaded with other dyes and/or pigments, for example with C.I. Direct Red 1, 11, 37, 62, 75, 81, 87, 89, 95 and 227; C.I. Acid Red 1, 8, 52, 87, 94, 115, 131, 144, 152, 154, 186, 245 and 249; C.I. Pigment Red 122, 57:1, 146, 176, 184, 185 and 269.
In the examples which follow, the lightfastness is determined according to DIN 54003 (blue wool scale). 1 is very low, 2 is low, 3 is moderate, 4 is fairly good, 5 is good, 6 is very good.